An early sketch by Seitu Jones
It's only a model
Rhino 3D wireframe
The flattened facets of the trunk
The trunk armature
2 powerhammer dies for curving the facets
The facets after hammering
The armature with half of the lower skin on
Tabs helped to align the halves
This strip was difficult to force into place
One way to cheat
The head again
Me and my dragon
Posted by Hal Eckhart at August 26, 2004 06:35 PM
This is a project that really gets me going. It's a sixteen foot tall dragon head clock tower designed by Seitu Jones
for the FAIR School
in Crystal. It's being produced by Art-Tech Productions
in Minneapolis, who hired me to do the metal work.
The tower is being constructed primarily from CorTen Steel, the rusty-looking stuff you see nowadays on big power poles, bridges, and sculpture. The small amount of copper in the steel makes it the surface oxidize very quickly, and then protects it against further corrosion.
The only thing really difficult about this project is the tapered, curving trunk of the tower. (Perhaps it's actually a neck more than a trunk, but nobody's corrected me yet). Bending a tube that size (even if you could get it in CorTen) would be enough of a challenge, but it tapers from 9 inches down to 5, which would make bending it almost impossible without equipment I can't even dream of.
So I decided to construct it from two sets of 6 facets, calculating and exporting the shapes with Rhinoceros
, which has a couple of clever features that help in this situation.
The first is the ability to extrude a profile (called a curve in the program) along two "rails" (two curving lines, in this case) to create a flowing 3-dimensional shape. I used the option "do not simplify", which helps the next step work correctly.
The second clever feature that Rhino has to help me out here is "unroll developable surface". To use it. it's first necessary to "extract" the surfaces of the 3D object, which separates it into faces. Then, the unroll command flattens the face, and tells you how much distortion it caused. The distortion hasn't ever been a huge deal for me (if the command succeeds), but it can be difficult to get the faces pulled together.
One way that I've found to draw sheets together is this situation is to weld a pair of wide jaw vice-grip pliers to the steel, and then use another pair of the same sort of vice-grips to squeeze the first. Then I just tighten one after the other until the gap is close enough or the weld breaks. It's really amazing how well this works.
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